Rosalind is certainly shown to be smarter than David in this story. It is she, for example, who in Chapter 12 is shown to have predicted that they would need to leave sooner than they anticipated. She therefore, unlike David, spent a long time packing and preparing for their flight, whereas David anticipated having longer to prepare and therefore only packed a few scant supplies. Note what Rosalind says to David and mocks him for falling asleep when he should have been packing:

And so when I tried to consult you about it, there you were swinishly asleep. My mother and I spent two solid hours packing up these panniers and getting the saddles slung up ready for an emergency, while all you did was go on sleeping.

Rosalind is clearly a character who is able to recognise the threat of danger and act in a way that allows her to be best prepared for that danger. In this sense, she is clearly superior to David, who doesn't seem to have the same nack for understanding the danger he is in and the need to prepare for that danger adequately.